Doxycycline Host-directed Therapy to Improve Lung Function and Decrease Tissue Destruction in Pulmonary Tuberculosis

The recruitment target would be 150 patients, with 75 in each arm Inclusion criteria: Patients should meet all criteria: 1. Aged 21 years and above 2. Patients receiving ≤ 14 days of TB treatment or about to start standard combination TB treatment 3. Confirmed pulmonary TB with positive acid-fast bacilli smear and/or positive nucleic acid amplification test (NAAT) and/or TB culture results 4. CXR demonstrating pulmonary involvement with cavity or cavities 5. Able to provide informed consent Exclusion criteria: 1. HIV co-infection 2. Previous pulmonary TB 3. Severe, pre-existing lung disease such as pulmonary fibrosis, bronchiectasis, COPD and lung cancer 4. Pregnant or breast feeding 5. Allergies to tetracyclines 6. Patients on retinoic acid, neuromuscular blocking agents and pimozide which may increase risk of drug toxicity 7. Autoimmune disease and/or on systemic immunosuppressants 8. Use of any investigational or non-registered drug, vaccine or medical device other than the study drug within 182 days preceding dosing of study drug, or planned use during the study period 9. Enrolment in any other clinical trial involving a systemic drug or intervention involving the lung 10. Evidence of severe depression, schizophrenia or mania 11. ALT \> 3 times upper limit of normal 12. Creatinine \> 2 times upper limit of normal 13. Principal investigator assessment of lack of willingness to participate and comply with all requirements including follow-up of the protocol, or identification of any factor felt to significantly increase the participant's risk of suffering an adverse outcome